Dual actuator friction brake assembly

ABSTRACT

An industrial brake is provided through which tension and emergency braking are initiated at opposite axial ends of the brake in order to improve packaging and maintenance of the brake and to enable the addition of an emergency brake function to existing tension brakes without substantial modifications to the brake. The brake includes a housing disposed about a driven shaft and friction plates coupled to the housing and the shaft respectively. One friction plate comprises a liquid cooled fluid jacket. One end cap assembly is disposed at one axial end of the housing and provides a tension brake function. Another end cap assembly is disposed at the opposite axial end of the housing and provides an emergency brake function.

This application claims priority to and is a continuation of U.S. patentapplication Ser. No. 11/263,395 filed Oct. 31, 2005 now U.S. Pat. No.7,556,128, the entire disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to brakes and, more particularly, to a brake inwhich tension and emergency braking are initiated at opposite axial endsof the brake.

2. Disclosure of Related Art

A conventional water cooled disc brake includes a stationary housingdisposed about a rotating shaft. A plurality of friction plates arecoupled to the housing and fixed against rotation relative to thehousing, but axially moveable relative to the housing. These frictionplates define fluid jackets through which cooling liquids arecirculated. Another plurality of friction plates are coupled to theshaft for rotation therewith and are axially movable relative to theshaft. The plates coupled to the shaft are interleaved with the platescoupled to the housing. An emergency or safety brake actuator isdisposed at one axial end of the brake and applies a constant force inan axial direction to bring the plates into contact with one another. Atension brake actuator is disposed at the same axial end of the brakeand applies a variable force for controlled braking torque.

In some conventional brakes, the tension brake actuator applies a forcein the opposite axial direction relative to the emergency brake actuatorand controlled braking is accomplished by the combination of forces fromthe two actuators. In these brakes, however, the amount of tensionbraking force that can be applied and the ability to control the tensionbraking force are limited because of the need to offset the force of theemergency brake actuator. Commonly assigned U.S. Pat. No. 6,029,782discloses an improved brake in which an additional actuator is employedto counter the force applied by the emergency brake actuator. In thismanner, tension braking is made responsive solely to the tension brakeactuator. Although the brake in U.S. Pat. No. 6,029,782 represents animprovement relative to previous brake designs, the improved brakesuffers from packaging limitations and renders maintenance of the brakeactuators and other brake components relatively difficult. Further, thebrake design cannot be readily applied to modify existing brakes havingonly a tension brake actuator. Rather, substantial modifications to thebrake are required.

The inventors herein have recognized a need for a brake that willminimize and/or eliminate one or more of the above-identifieddeficiencies.

SUMMARY OF THE INVENTION

The present invention provides a brake having emergency and tensionbrake actuators disposed at opposite axial ends of the brake.

A brake in accordance with the present invention includes a housingdisposed about a driven shaft. The driven shaft rotates about arotational axis. The brake further includes a first friction platecoupled to the driven shaft for rotation therewith and axially movablerelative to the shaft. The brake also includes a second friction platecoupled to the housing and fixed against rotation relative to thehousing, but axially movable relative to the housing. The secondfriction plate defines a fluid jacket configured for passage of a fluid.The brake further includes a first end cap assembly disposed at a firstaxial end of the housing and coupled to the housing. The first end capassembly includes a first pressure plate and means for applying avariable control force to the first pressure plate to urge the firstpressure plate in a first axial direction towards the first and secondfriction plate. The brake further includes a second end cap assemblydisposed at a second axial end of the housing. The second end capassembly is coupled to the housing and includes a second pressure plate.The second cap assembly also includes means for applying a setting forceto the second pressure plate in a second axial direction to urge thesecond pressure plate towards the first and second friction plates andmeans for selectively applying a release force in the first axialdirection against the setting force.

A brake in accordance with the present invention has significantadvantages relative to conventional brakes. First, packaging of thebrake is improved by locating the tension and emergency brake actuatorsat opposite axial ends of the brake. Second, accessibility formaintenance is improved. Finally, existing brakes employing only tensionbrakes can be easily modified to incorporate emergency brake functions.

These and other advantages of this invention will become apparent to oneskilled in the art from the following detailed description and theaccompanying drawings illustrating features of this invention by way ofexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a split cross-sectional view of a brake in accordance with thepresent invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Referring now to the drawings wherein like reference numerals are usedto identify identical components in the various views, FIG. 1illustrates a brake 10 in accordance with the present invention. Brake10 may be provided for heavy duty industrial use (e.g., on oil drillingequipment). Brake 10 includes a housing 12, two sets of friction plates14A-E, 16A-D, and end cap assemblies 18, 20. Brake 10 may also include aspacer 22.

Housing 12 provides structural support to the other components of brake10. Housing 12 may be made from conventional metals, metal alloys and/orplastics. Housing 12 is disposed about a driven shaft 24 and may becentered about the rotational axis 26 of the shaft 24. Housing 12 may besubstantially circular in shape and unitary in construction or composedof multiple pieces joined together. Housing 12 defines axially extendingbores 28, 30 at either end configured to receive fasteners 32, 34 usedto connect end cap assemblies 18, 20, respectively, to housing 12.Housing 12 also defines a plurality of radial openings 36 sized forreceipt of hoses and connectors (not shown). Housing 12 includes aplurality of spline teeth 38 on a radially inner surface for a purposedescribed hereinbelow. One or more mounting brackets 40, 42 or feet, mayextend from housing 12 to allow brake 10 to be mounted to a surfaceextending substantially parallel to axis 26.

Friction plates 14A-E are provided to transmit a braking torque tofriction plates 16A-D and to shaft 24 upon engagement of plates 14A-E,16A-D. Friction plates 14A-E may include a plurality of spline teeth 44disposed on radially outer surfaces of plates 14A-E that are configuredto mate with teeth 38 of housing 12 thereby preventing relative rotationof plates 14A-E relative to housing 12, but allowing axial movement ofplates 14A-E relative to housing 12. Friction plates 14A-E may be biasedapart by springs 46 that are disposed between each pair of plates 14A-Eand are disposed about pins 48 extending through plates 14A-E. Althoughfive friction plates 14A-E are shown in the illustrated embodiment, itshould be understood that the number of friction plates can be varied tovary braking torque. Each of friction plates 14A-E includes one or moreplates 50 and a fluid jacket 52.

Plates 50 are conventional in the art and may be made from a variety ofconventional metals and metal alloys including iron or copper. Plates 50may be connected to one or both sides of each fluid jacket 52 usingfasteners 54 such as bolts or screws or pins.

Fluid jackets 52 are provided to allow for circulation of a coolingliquid such as water or another conventional liquid within brake 10 toallow for transfer of frictional heat generated within brake 10. Jackets52 are conventional in the art and include an annular body that definesa fluid manifold through which liquid circulates and which provides asurface on which plates 50 are mounted. Jackets 52 may define aplurality of concentric flow passages 56 and radial flow passages 58that place concentric passages 56 in fluid communication with fluidinlets 60 and outlets (not shown).

Friction plates 16A-D are provided to transfer braking torque fromfriction plates 14A-E to shaft 24. Friction plates 16A-D may be madefrom conventional metals and metal alloys such as iron and copper.Plates 16A-D include a plurality of spline teeth 64 at a radially innersurface that are configured to engage with teeth 66 of shaft 24 (or ahub mounted to shaft 24) to couple friction plates 16A-D to shaft 24.Plates 16A-D may include a conventional friction material 68 connectedto each side of plate 16A-D by fasteners 70 such as bolts or screws.Again, although four plates 16A-D are shown in the illustratedembodiment, it should be understood that the number of plates 16 can bevaried to vary braking torque.

End cap assembly 18 closes one axial end of housing 12 and providessupport for a tension brake actuator. End cap assembly 18 includes anend plate 72, a pressure plate 74, and means, such as bladder 76, forapplying a variable control force to pressure plate 74 to urge pressureplate 74 in an axial direction (to the left in FIG. 1) towards frictionplates 14A-E, 16A-D.

End plate 72 is annular in construction and is fastened to housing 12using one or more fasteners 32. Plate 72 defines an annular recess 78configured to receive bladder 76. Plate 72 also defines an axial bore 80through which pneumatic or hydraulic fluid is provided to bladder 76 viaa hose (not shown).

Plate 74 is provided to compress plates 14A-E, 16A-D to create a brakingtorque on shaft 24. Plate 74 is conventional in the art and may be madefrom conventional metals and metal alloys. Plate 74 is annular inconstruction.

Bladder 76 provides a means for applying a variable control force toplate 74 and serves as a tension brake actuator. Bladder 76 isconventional in the art. When fluid is supplied to bladder 76, bladder76 expands and urges pressure plate 74 in an axial direction (to theleft in FIG. 1) against the force of springs 46 to compress, and causeengagement of, friction plates 14A-E, 16A-D. When fluid pressure isremoved from bladder 76, springs 46 bias friction plates 14A-E, 16A-Dapart.

End cap assembly 20 closes an opposite axial end of housing 12 andprovides support for a safety or emergency brake actuator. End capassembly 20 includes an end plate 82, a pressure plate 84, means, suchas springs 86, for applying a setting force to pressure plate 84 in anaxial direction (to the right in FIG. 1) to urge pressure plate 84towards friction plates 14A-E, 16A-D, and means, such as piston 88 andone or more fasteners 90, for selectively applying a release force in anopposite axial direction (to the left in FIG. 1) against the settingforce.

End plate 82 is annular in construction and is fastened to housing 12using one or more fasteners 34. Plate 82 defines an annular recess 92configured to receive plate 84. Plate 82 further defines a plurality ofrecesses 94 opening into recess 92. Each recess 94 is configured toreceive one end of a spring 86.

Pressure plate 84 is provided to compress plates 14A-E, 16A-D to createa braking torque on shaft 12. Plate 84 is conventional in the art andmay be made from conventional metals and metal alloys. Plate 84 isannular in construction and defines one or more stepped diameter bores96 configured to receive corresponding fasteners 90. Plate 84 may alsodefine one or more recesses 98 on a side of plate 84 opposite frictionplates 14A-E, 16A-D. Each recess 98 is configured to receive one end ofa corresponding spring 86.

Springs 86 provide a means for applying a setting force against pressureplate 84 to urge plate 84 in an axial direction (to the right in FIG. 1)to compress plates 14A-E, 16A-D. Springs 86 are disposed within recesses94, 98 in end plate 82 and pressure plate 84, respectively. Springs 86are conventional in the art any may comprise coil springs or otherconventional springs. Springs 86 may be circumferentially spaced aboutaxis 26 and may be disposed at varying radial distances from axis 26.

Piston 88 selectively urges fasteners 90 and plate 84 in an axialdirection (to the left in FIG. 1) against the setting force of springs86. Although a single, annular piston 88 is shown in the illustratedembodiment, multiple pistons 88 could be employed. Piston 88 is disposedon one side of end plate 82 opposite pressure plate 84. Piston 88defines one more through bores 100 through which fasteners 90 extend.Piston 88 also defines one or more fluid chambers 102 opening in thedirection of end plate 82. A body 104 (or bodies) may be disposed in thefluid chamber 102 (or chambers 102), bearing against end plate 82. Aseal (not shown) disposed between body 104 and the walls of chamber 102prevents fluid leakage.

Fasteners 90 couple pressure plate 84 and piston 88 for movementtogether. Fasteners 90 may extend through pressure plate 84, end plate82 and piston 88 and may include a female part 105 and a male part 106.In the illustrated embodiment, each female part 105 has a steppeddiameter at one end configured to be received within bores 96 inpressure plate 84. Male part 106 extends into female part 105 and issecured for movement with female part 105. Male part 106 includes a headthat bears against the outer surface of piston 88.

Brake 10 is released by providing fluid to chambers 102. The expandingfluid volume within chambers 192 causes piston 88 to move away from endplate 82 in an axial direction (to the left in FIG. 1) against the forceof springs 86. Piston 88 pulls fasteners 90 and pressure plate 84 in thesame direction. When fluid pressure is removed from chambers 102,springs 86 force pressure plate 84 in the opposite axial direction (tothe right in FIG. 1) to reset the brake 10, returning piston 88 to itsoriginal position.

Spacer 22 provides means for adjusting an axial position of end capassembly 20 relative to housing 12. Although spacer 22 is illustrated inFIG. 1 for use in adjusting the axial position of end cap assembly 20relative to housing 12, it should be understood that spacer 22 could beemployed on the opposite side of brake 10 to allow adjustment of theaxial position of end cap assembly 18 relative to housing 12. Spacer 22may comprise one or more shims disposed between end cap assembly 20 andhousing 12. The shims may be disposed about the circumference, or aportion of the circumference, of fasteners 34. As the brake wears,fasteners 34 may be loosened to allow removal of one or more shimsthereby enabling end cap assembly 20 to be drawn closer to housing 12and to compensate for wear.

A brake in accordance with the present invention has significantadvantages relative to conventional brakes. First, packaging of thebrake is improved by locating the tension and emergency brake actuatorsat opposite axial ends of the brake. Second, accessibility formaintenance is improved. Finally, existing brakes employing only tensionbrakes can be easily modified to incorporate emergency brake functions.

While the invention has been shown and described with reference to oneor more particular embodiments thereof, it will be understood by thoseof skill in the art that various changes and modifications can be madewithout departing from the spirit and scope of the invention.

1. A brake, comprising: a housing disposed about a driven shaft, said driven shaft rotating about a rotational axis; a first friction plate coupled to said driven shaft for rotation therewith and axially movable relative to said driven shaft; a second friction plate coupled to said housing and fixed against rotation relative to said housing, but axially movable relative to said housing, said second friction plate defining a fluid jacket configured for passage of a fluid; a first end cap assembly disposed at a first axial end of said housing and coupled to said housing; said first end cap assembly including a first pressure plate; and, means for applying a variable control force to said first pressure plate to urge said first pressure plate in a first axial direction towards said first and second friction plates; a second end cap assembly disposed at a second axial end of said housing and coupled to said housing, said second end cap assembly including: a second pressure plate; means for applying a setting force to said second pressure plate in a second axial direction to urge said second pressure plate towards said first and second friction plates; and, means for selectively applying a release force in said first axial direction against said setting force wherein said fluid flows within and through said second friction plate.
 2. The brake of claim 1 wherein said means for applying a variable control force and said means for applying a setting force are separately controllable.
 3. The brake of claim 2, further comprising a mounting bracket extending radially from said housing.
 4. The brake of claim 2 wherein said means for applying a variable control force includes an expandable fluid bladder.
 5. The brake of claim 4 wherein said bladder is disposed against said pressure plate.
 6. The brake of claim 2 wherein said setting means includes a plurality of springs.
 7. The brake of claim 6 wherein said springs are circumferentially spaced.
 8. The brake of claim 1, further comprising a mounting bracket extending radially from said housing.
 9. The brake of claim 1 wherein said means for applying a variable control force includes an expandable fluid bladder.
 10. The brake of claim 9 wherein said bladder is disposed against said pressure plate.
 11. The brake of claim 1 wherein said setting means includes a plurality of springs.
 12. The brake of claim 11 wherein said springs are circumferentially spaced.
 13. The brake of claim 1 wherein said means for applying a release force includes: a piston disposed on an opposite side of an end plate of said second end cap assembly relative to said second pressure plate, said piston defining a fluid chamber; a fastener extending through said end plate and coupling said piston and said second pressure plate; wherein fluid pressure provided to said fluid chamber causes movement of said piston in said second axial direction and corresponding movement of said fastener and said second pressure plate.
 14. The brake of claim 1, further comprising a spacer disposed between said housing and one of said first and second end cap assemblies.
 15. The brake of claim 14 wherein said spacer comprises a plurality of shims.
 16. The brake of claim 14 wherein said spacer is disposed about a fastener coupling said one end cap assembly to said housing. 